Django admin searchfield with GenericForeignKey

Question

My Django Foo model has the following GenericForeignKey:

content_type = models.ForeignKey(ContentType, blank=True, null=True, on_delete=models.SET_NULL)
    object_id = models.PositiveIntegerField(blank=True, null=True)
    my_object = GenericForeignKey('content_type', 'object_id')

my_objects can be instances of Baz and (rarely) Qux models. The Qux model has a foreign key to Baz. I want to have a searchfield in my Foo admin page that would search by baz_id and yield either instances of Foo that have the Baz of the given ID in my_object field or instances of Foo that have Qux related to the Baz of the given ID.

Here's what I'm trying to do:

class FooAdmin(...): 
# some custom classes and mixins here, neither of which overrides get_search_results()
    query_fields_placeholders = {'object_id': 'Baz ID'}
    ...
    ...
    search_fields = ('object_id',)
    
        def get_search_results(self, request, queryset, search_term):
        queryset, use_distinct = super().get_search_results(request, queryset, search_term)
        if search_term:
            baz_content_type = ContentType.objects.get_for_model(Baz)
            qux_content_type = ContentType.objects.get_for_model(Qux)

            baz_queryset = queryset.filter(
                content_type=baz_content_type, object_id=search_term
                )

            related_qux_ids = Subscription.objects.filter(baz_id=search_term).values_list(
                    'id', flat=True
                )
            qux_queryset = queryset.filter(
                    content_type=qux_content_type, object_id__in=related_qux_ids
                )

            queryset = baz_queryset | qux_queryset

        return queryset, use_distinct

However, what happens is that only Foo instances that have Baz instances as my_objects are returned by the search and those that have Qux instances in my_object fields seem completely ignored (as if the qux_queryset part didn't exist at all). Everything looks fine if I just run all these queries in a Django shell or check the underlying SQL, but Django Admin itself seems to somehow interfere with my search.

Any suggestions?